Vertebral cage device with modular fixation

ABSTRACT

Intervertebral arthrodesis for insertion in an intervertebral space separating opposite faces of two adjacent vertebrae has a ring shaped intervertebral cage having a small bar that extends parallel to the axis of the spine. The bar has a height less than the rest of the cage. A surface of the cage contacting the vertebrae has an undulating shape for limiting sliding of the cage in a plane parallel to the vertebrae faces.

[0001] The present invention concerns an arthrodesis device, used to enable fusing of two contiguous vertebrae by development of bony tissues with replacement of fibrocartilaginous discs ensuring the bonding between the vertebrae of the vertebral column or the end of the latter.

[0002] The intervertebral discs are formed from a deformable but not compressible part called “nucleus pulposus” containing approximately 80% water, surrounded by several elastic fibrous layers uniting to maintain the nucleus, absorbing part of the forces applied to the disc unit, and stabilizing the articulation. These parts may often be degraded by compression, displacement or wear and tear, following shocks, infections, exaggerated forces or simply over time. The degradation of this articulation part may cause intense pain in the patient and significant discomfort.

[0003] In a good number of cases, the treatment consists of removing all or part of the damaged intervertebral disc and connecting the vertebrae concerned by causing bony fusion between them. To do that, one places between the vertebrae an artificial structure allowing their separation to be maintained, while with it introducing into the intervertebral space either a bony graft or a bony substitute, compounded material that will be invaded by the growth of adjacent bony tissues. This structure often takes the shape of an open or closed ring called cage, and may be positioned on the basis of a cage by the intervertebral space in the case of cervical vertebrae, or on the basis of one or two cages by the intervertebral space in the case of lumbar vertebrae. This positioning is done most often by the anterior surface of the vertebrae in the case of a cervical cage, or by the anterolateral surface of the vertebrae (one cage) or posterior (two cages) of vertebrae in the case of a lumbar cage. As for grafts and bony substitutes, they are introduced in the cage either before or after its positioning and are therefore found in contact with the two vertebrae surrounding the treated intervertebral space.

[0004] During the time necessary for growth and up to the reinforcement of arthrodesis, which may be on the order of six months, it is important that the various movements of forces taking place in the intervertebral space do not cause displacement of the cage, which would then risk deteriorating the bony tissues during formation or even escaping outside this space and damaging the adjacent organs.

[0005] To avoid such displacements, a solution used consists of equipping the surfaces of the cage in contact with the vertebrae with varieties of shape such as saw tooth notches as described in the patents FR0006351 or FR2733413. Such a solution however proves to be insufficient in a certain number of cases.

[0006] Another solution consists of equipping the cage with a flange that extends on the outside of the intervertebral space and is applied on the side of each of the two contiguous vertebrae, to which it is fixed by a bone anchoring screw. Such a solution has been used since about 1988 and is described for example in the patent FR 2 747 034. Such a plate however represents an overcrowding outside the intervertebral space that sometimes may pose problems in particular in the case of arthrodesis of the cervical vertebrae where the space available is very limited. In fact, the presence of the plate may for example form a daily discomfort for the patient or form an immediate or future obstacle in the positioning of another cage with plate in one of the immediately adjacent plates.

[0007] Furthermore, in particular in the case of cervical vertebrae, the movements of the spine often have the tendency to cause loosening of the bone anchoring screws, which decreases the effectiveness of such a plate and may also cause damages to the organs surrounding the plate.

[0008] Therefore, it is worthwhile to also provide for a system enabling fixation of the cage without a part extending outside the intervertebral space.

[0009] Moreover, these different solutions may fulfil the needs of an arthrodesis operation differently without it being necessarily possible to know in advance which will be preferable. Therefore, it is easier and less expensive to provide for a modular device comprising interchangeable parts for achieving different solutions.

[0010] To remedy some of these drawbacks, the present invention proposes an intervertebral arthrodesis device designed to be inserted in an intervertebral space separating the opposite plates of the two adjacent vertebrae, characterised in that it comprises at least one structure called intervertebral cage presenting the shape of a ring that may or may not be open, in which at least one part, along the axis of the spine, has a lower height than the rest of this same cage and forms a small bar crossed by at least one drilling of the axis approximately perpendicular to the plate of at least one of the adjacent vertebrae.

[0011] According to one characteristic, the device is characterised in that at least one intervertebral cage includes on its surfaces in contact with the vertebrae, variations in shape limiting its possibilities for sliding in a plane parallel to said vertebrae.

[0012] According to one characteristic, the device is characterised in that it comprises fixation means of the cage(s) to at least one of these vertebrae, these fixation means being able to be added to at least one intervertebral cage by insertion of a projecting part in at least one drilling of the cage.

[0013] According to one characteristic, the device is characterised in that the fixation means comprise at least two bone anchoring pins with approximately parallel axes connected by small rod, these anchoring pins pushed in the plate of at least one vertebra and inserting in at least one drilling of at least one intervertebral cage to keep this same cage in position in the intervertebral space.

[0014] According to one characteristic, the device is characterised in that at least one of the bone anchoring pins of fixation means includes reliefs limiting the possibilities of sliding outside the plate where it is impacted.

[0015] According to one characteristic, the device is characterised in that the fixation means comprise at least one fixation plate fixed to the external surface of at least one vertebra and including at least one drilling receiving a bone anchoring screw fixed to this same vertebra.

[0016] According to one characteristic, the device is characterised in that at least one of the drillings of the fixation plate presents in the plane of this plate a section at the level of its opening opposite the vertebra that is not as high as in its part located within the thickness of the plate, this drilling through which is inserted a bone anchoring screw the head of which presents at least one part of a section greater than that of this opening of the drilling and is thus retained within this same drilling by this same external opening.

[0017] According to one characteristic, the device is characterised in that the fixation means include at least two locking studs with approximately parallel axes connected by a small rod, these locking studs inserting in at least one drilling of at least one intervertebral cage to lock these same fixation means to this same cage and to keep it in position in the intervertebral space.

[0018] According to one characteristic, the device is characterised in that at least one of the ends of the small rod presents at least one protuberance clipped in at least one housing arranged in the wall of the intervertebral cage so as to limit or prevent the movements of this same rod relative to this same cage.

[0019] According to one characteristic, the device is characterised in that the fixation means comprise a fixation plate called hemiplate coupled to the exterior surface of at least one vertebra, this plate including at least one drilling through which is inserted a bone anchoring screw fixed in said vertebra to keep this same cage in position in the intervertebral space.

[0020] According to one characteristic, the device is characterised in that the fixation hemiplate with the small rod connecting the anchoring pins or the locking studs forms a piece with an “L” section.

[0021] According to one characteristic, the device is characterised in that the fixation means comprise a fixation plate called complete coupled to the exterior surface of at least two vertebrae, this plate including near each end at least one drilling through which is inserted a bone anchoring screw fixed in said vertebrae to prevent any migration of the intervertebral cage within or outside the intervertebral space.

[0022] According to one characteristic, the device is characterised in that the complete fixation plate with the small rod connecting the anchoring pins or the locking studs a piece with a “T” section.

[0023] According to one characteristic, the device is characterised in that the fixation plate includes an opening at the level of the intervertebral space, this opening enabling the introduction or packing of graft or bone substitute in this intervertebral space after insertion of the device.

[0024] According to one characteristic, the device is characterised in that each drilling of the fixation means acting together with a bone anchoring crew, once in place, is located in a position shifted relative to a plane containing the axis of the spine.

[0025] According to one characteristic, the device is characterised in that at least one intervertebral cage presents, along the axis of the spine, a nonuniform height, this variation in height inducing a determined angle between the plates in respect to the adjacent vertebrae.

[0026] According to one characteristic, the device is characterised in that at least one of its constitutive parts is a made from a radiotransparent material.

[0027] The invention, with its characteristics and advantages, will be more clearly evident with the reading of the description made in reference to the fixed drawings in which:

[0028]FIG. 1a represents a side sectional view of the device according to the invention in an embodiment where the fixation device comprises anchoring pins and a top hemiplate;

[0029]FIG. 1b represents a side sectional view of the device according to the invention in an embodiment where the fixation device comprise a complete plate, with opening, added by locking studs and with anchoring screws retained in the drillings of the plate;

[0030]FIG. 2 represents a top sectional view of the device according to the invention in an embodiment where the fixation device comprises anchoring pins and a low hemiplate;

[0031]FIG. 3a represents a view in perspective of an intervertebral cage according to the invention;

[0032]FIG. 3b represents a view in perspective of a device according to the invention before impacting pins in an embodiment where the fixation device comprises anchoring pins with variations in shape;

[0033]FIG. 3c represents a view in perspective of a device according to the invention before impacting “V” shape tongues in an embodiment where the fixation device comprises anchoring “V” shape tongues;

[0034]FIG. 4a represents a view in perspective of a device according to the invention in an embodiment where the fixation device comprises anchoring pins and a low hemiplate;

[0035]FIG. 4b represents a view in perspective of a device according to the invention in an embodiment where the fixation device comprises anchoring pins and a top hemiplate with opening;

[0036]FIG. 5a represents a view in perspective of a device according to the invention in an embodiment where the fixation device comprises anchoring pins and a complete plate with opening;

[0037]FIG. 5b represents a view in perspective of a device according to the invention in an embodiment where the fixation device comprises a complete plate added by locking studs, illustrated with anchoring screws.

[0038] In one embodiment, an arthrodesis device according to the invention comprises at least one intervertebral cage (1) in the shape of a ring, designed to be inserted in the intervertebral space (E) to be treated between two contiguous vertebrae, and to be received into an interior cavity (10, FIG. 2a) a bony material acting as a graft, or any structure that may act as a bony substitute or be “assembled” by a growth of bony material. The cavity of the intervertebral cage may thus be filled before or after its positioning in the intervertebral space.

[0039] According to the applications, the device according to the invention may include a single intervertebral cage (1, FIGS. 1 and 2a), for example to carry out arthrodesis between two cervical vertebrae.

[0040] According to the applications, the device according to the invention may include two intervertebral cages (not represented) for example to carry out arthrodesis between two lumbar vertebrae during positioning by the posterior route.

[0041] According to the applications, an intervertebral cage according to the invention may be made in the shape of a closed ring (1, FIG. 3a) or in the form of a ring opened on one side (not represented).

[0042] In one embodiment represented in FIGS. 1 and 2a, the invention comprises a fixation device enabling its anchoring in the plate (V0) of a vertebra (V) within the intervertebral space (E) to be treated. This fixation device is formed from two anchoring pins (21, 22), with approximately parallel axes and connected by a small rod (23). These anchoring pins are introduced into two drillings (121, 122) made in a thinned down part of the intervertebral cage, then are impacted, that is pushed in with force, into the bony material forming the plate of one of the two vertebrae surrounding the intervertebral space to be treated.

[0043] In one embodiment, the thinned down part of the cage forms a small flat rod (12) on which the small rod (23) is abutted, it is also flat, connecting the two anchoring pins (21, 22) when the latter are impacted in the plate (V0) of a vertebra (V). The thickness of the small rod (23) connecting the anchoring pins and the small rod (12) formed by a thinning of the intervertebral cage (1) are determined so that the superimposition of the two small rods (12, 23) after impacting are not higher along the axis of the spine than the rest of the intervertebral cage (1).

[0044] In one embodiment represented in FIG. 3b the length of the anchoring pins (21, 22) and the thickness of the small rod (23) connecting them are determined so that the sum of these two dimensions forming the height of the fixation device in this embodiment is not greater than the height along the axis of the spine of the rest of the intervertebral cage (1). Thus, it is possible to introduce into this intervertebral space an intervertebral cage already provided with anchoring pins, the latter then only having been impacted into the plate (VO) of a vertebra (V) for example with the aid of a spreader, a distractor or another tool of known type.

[0045] In one embodiment represented in FIG. 3c, the fixation device, enabling the device anchoring in the plate (V0) of a vertebra (V) within the intervertebral space (E) to be treated, is constituted of two “V” shape anchoring tongues (51, 52), connected by a small rod (53). These anchoring tongues (51, 52) are introduced between a thinned down part of the intervertebral cage forming a small rod (62) and two lugs (only one, 54, is represented on FIG. 3c) formed on the device and symmetrically disposed in relation to the device axis. The “V” shape anchoring tongues (51, 52) are then impacted, as in the case of the device provided with pins (21, 22), and the small flat rod (53), connecting the two “V” shape anchoring tongues (51, 52) can abut on the small rod (62), also flat, when the tongues are impacted impacted in the plate (V0) of a vertebra (V). The thickness of the small rod (53) connecting the anchoring tongues and the small rod (62) formed by a thinning of the intervertebral cage (1) are determined so that the superimposition of the two small rods (62, 53) after impacting are not higher along the axis of the spine than the rest of the intervertebral cage (1).

[0046] In one embodiment (not represented), the device according to the invention comprises two intervertebral cages. These two cages are each formed from an open ring in which at least part presents a reduction in height along the axis of the spinal cord. In one embodiment, at least one of these same cages is in the shape of a “U” or “C” (not represented) and each includes at its end a small rod from one part presenting a reduction in height along the axis of the spine. These small rods are crossed by at least one drilling with axis approximately perpendicular to the plate (V0) of the vertebra (V) with which they are in contact. In one embodiment, two intervertebral cages are arranged in the intervertebral space with their openings facing each other and at least one fixation device including two anchoring pins with parallel axes connected by a small rod is introduced into the drilling of each of the two small rods with ends facing each other. The anchoring pins are then impacted in the plate of the vertebra and insert in the drillings of the small rods of the intervertebral cages to help to keep said cages immovable.

[0047] In one embodiment, an intervertebral cage (1) used in a device according to the invention includes on at least one of its surfaces in contact with the vertebrae (V) variations in shape (11) for example, in saw tooth [misspelled word; shape]. Under the pressure exerted by the vertebrae surrounding the treated intervertebral space (E), these variations in shape are supported on the surface of the plates (V0) of these same vertebrae and thus limit the risks of displacement of this same intervertebral cage.

[0048] In one embodiment represented in FIGS. 1, 2a and 4 b a fixation device used in the device according to the invention comprises a plate called top hemiplate (32) united with the small rod (23) connecting the anchoring pins (21, 22) to each other, which extends outside the intervertebral space (E) to be treated and is coupled to the exterior surface of the vertebra opposite the vertebra receiving the anchoring pins. This top hemiplate includes at least one drilling (321) which receives a bone anchoring screw (4) of a known type, this screw (4) being fixed in the body of the vertebra and inserting in the plate to prevent any migration of the intervertebral cage (1) within or outside the treated intervertebral space (E). This top hemiplate also comprises an opening (320) enabling introduction of the graft into the cage (1) after its positioning in the intervertebral space. The part of the piece connecting the small rod (23) and the top hemiplate (32) then presents an “L” shape.

[0049] In one embodiment represented in FIG. 4a, a plate called bottom hemiplate (31) is fixed in the same way to the vertebra receiving the anchoring pins. The part of the piece connecting the small rod (23) and the bottom hemiplate (31) then presents an “L” shape.

[0050] In one embodiment represented in FIG. 5a, a fixation device used in the device according to the invention comprises a plate called complete plate (33) integral with the small rod (23) connecting the anchoring pins (21, 22) to each other, which extends to the exterior of the intervertebral space (E) to be treated and is coupled to the exterior surface of these two vertebrae surrounding the intervertebral space (E) to be treated. The part of the piece connecting the small rod (23) and the complete plate (33) then presents a “T” shape. This complete plate (33) includes at least two drillings (331, 332) which each receive a bone anchoring screw (4) of a known type, this screw (4) being fixed in the body of the corresponding vertebra and inserting in the plate to prevent any migration of the intervertebral cage (1) within or outside the treated intervertebral space (E). This complete plate also comprises an opening (330) enabling introduction of the graft into the cage (1) after its placement in the intervertebral space.

[0051] In one embodiment represented in FIGS. 1b and 5 a, a fixation device used in the device according to the invention comprises a plate called complete plate (33) united with the small rod (23), this small rod including two locking studs (24, 25) perpendicular to its longitudinal axis and which is housed in the two drillings (121, 122) of the intervertebral cage (1). This complete plate (33) extends outside the intervertebral space (E) to be treated and it coupled to the exterior surface of the two vertebrae surrounding the intervertebral space (E) to be treated. The fact of using locking studs rather then pins makes it possible to use a material that would not be as hard to be impacted into the plate of the vertebra, but on the other hand presents the advantage of being transparent during radiography. The part of the piece connecting the small rod (23) and the complete plate (33) then presents a “T” shape in its section along a plane containing the axis of the spine.

[0052] This complete plate (33) includes at least two drillings (331, 332) which each receive a bone anchoring screw (4) of a known type, this screw (4) being fixed in the body of the corresponding vertebra and inserting in the plate to prevent any migration of the intervertebral cage (1) within or outside the treated intervertebral space (E).

[0053] In one embodiment represented in FIG. 5a, the small rod (23) connecting the locking studs and the complete plate (33) presents at its two ends in contact with the walls of the intervertebral cage (1) a rounded protuberance being clipped by elastic deformation in a housing (13) arranged in the wall opposite the intervertebral cage (1). The clipping of the protuberances (233) in the housings (13) makes it possible to maintain the cage (1) and the plate (33) together during positioning of the unit or after positioning.

[0054] In one embodiment, so as to avoid anchoring screws from loosening for example under the effect of the movements of the spine, the drillings of the plate (33) receiving the screws in a plane parallel to the plate present a section slightly lower than the interior of the plate at the level of their opening on the surface opposite the vertebra, called external. The head of the screws presents a part of a section greater than that of the external opening of the drilling. Thus, once screwed to where the large part of the head of the screw had penetrated the interior of the drilling under force, the elasticity of the material forming the plate will retain this head within the drilling, limiting the risks of later loosening. This complete plate also comprises an opening (330) enabling introduction of the graft into the cage (1) after its positioning in the intervertebral space.

[0055] In one embodiment the plate (31, 32, 33) of the fixation device according to the invention includes at least one of its drillings (311, 321, 331, 332) receiving a bone anchoring screw (4) which is located in a position shifted relative to a plane containing the axis of the spine. Thus, it is possible to treat two adjacent intervertebral spaces by using fixation plates and by positioning these plates in staggered rows, the shifted position of their drillings enabling them to be fixed by different screws located on the same vertebra and at the same height along the axis of the spine.

[0056] In one embodiment, all or part of the device according to the invention is made from a radiotransparent material, for example from PEEK, which makes it possible to monitor the development of bony tissues within the cage by radiography. In spite of that, for verification that the elements of the device are not displaced, it is possible to fix on one or more of the elements a radio marker containing for example a small piece of non-radiotransparent material.

[0057] Therefore, according to the applications it is possible to position an intervertebral cage (1) in different ways, simply by using one type or another of fixation device. The same intervertebral cage (1) may for example be positioned:

[0058] either alone,

[0059] or provided with a fixation device with pins (21, 22, 23),

[0060] or provided with a fixation device with pins and with a top (32) or bottom (33) hemiplate,

[0061] or provided with a fixation device with pins and with a complete plate (33),

[0062] or provided with a top (32) or bottom (31) hemiplate added by locking studs (24, 25),

[0063] or provided with a complete plate (33) added by locking studs (24, 25).

[0064] Such modularity may make it possible for the surgeon to choose the type of fixation during the surgery and according to the anatomic conditions he encounters, by having at his disposal a reduced number of components among which to choose.

[0065] It is also to be noted that the fixation device that is concerned for example with pins or a plate or both, may be later removed without significant destruction of the arthrodesis carried out, for example during a new surgery. In fact, this device may no longer be necessary after reinforcement of the arthrodesis, although forming discomfort, either for the patient or for similar treatment of an adjacent intervertebral space.

[0066] It must be obvious for persons skilled in the art that the present invention makes possible embodiments under numerous other specific forms without leaving the field of application of the invention as claimed. As a result, the present embodiments must be considered as illustration, but may be modified in the field defined by the scope of the fixed claims, and the invention must not be limited by the details given above. 

1-15 are canceled.
 16. Intervertebral arthrodesis device having a size and shape for insertion in an intervertebral space separating opposite faces of two adjacent vertebrae comprising at least one ring shaped intervertebral cage having a small bar adapted to extend parallel to the axis of the spine, the bar having a height less than the rest of the cage.
 17. Device according to claim 16 wherein the ring is closed.
 18. Device according to claim 16 wherein the ring includes an open segment.
 19. Device according to claim 16 wherein the at least one intervertebral cage includes on its surfaces adapted to contact the vertebrae an undulating shape for limiting sliding of the cage in a plane parallel to the faces of said vertebrae.
 20. Device according to claim 16 wherein the at least one cage includes a fixation structure for securing the at least one cage to at least one of the vertebrae, the fixation structure being arranged to be added to the at least one intervertebral cage by inserting a projecting part in at least one opening extending through the small bar, the at least one opening having an axis approximately perpendicular to the face plate of at least one of the adjacent vertebrae while the cage is inserted in the intervertebral space.
 21. Device according to claim 20 wherein the fixation structure comprises at least two bone anchoring pins having approximately parallel axes adapted to be inserted through a small rod and the openings of the small bar and pushed into the plate of at least one vertebra to keep said cage in position in the intervertebral space.
 22. Device according to claim 21 wherein at least one of the bone anchoring pins includes reliefs for limiting sliding of the cage outside the face to which the cage is fixedly secured.
 23. Device according to claim 21 wherein the fixation structure comprises at least one fixation plate adapted to be coupled to an external surface of at least one vertebra and including at least one opening for receiving a bone anchoring screw adapted to be fixed to the vertebra having the external surface.
 24. Device according to claim 23 wherein at least one of the openings of the fixation plate has, in the plane of the plate, a section that at the level of its opening opposite the vertebra that is lower in its part located within the thickness of the plate, a bone anchoring screw adapted to be inserted through the at least one opening of the fixation plate, the bone anchoring screw having a head with a cross section greater in area than that of the opening for enabling the screw to be retained within the opening.
 25. Device according to claim 20 wherein the fixation structure includes at least two locking studs with approximately parallel axes connected by a small rod, the locking studs being insertable into at least one opening of at least one intervertebral cage to lock the fixation structure to the cage and to keep the cage in position in the intervertebral space.
 26. Device according to claim 25 wherein at least one of the ends of the small rod has at least one protuberance clipped in at least one housing arranged in the wall of the intervertebral cage for limiting or preventing movements of said rod relative to said cage.
 27. Device according to claim 16 wherein the fixation structure comprises a fixation hemiplate coupled to the exterior surface of at least one vertebra, the fixation hemiplate including at least one opening through which is inserted a bone anchoring screw for attachment in said vertebra to keep said cage in position in the intervertebral space.
 28. Device according to claim 27 wherein the fixation hemiplate with a small rod connecting the anchoring pins or the locking studs forms a piece with an “L” section.
 29. Device according to claim 16 wherein the fixation structure comprises a complete fixation plate adapted to be coupled to the exterior surface of at least two vertebrae, the complete fixation plate including near each end at least one opening through each of which is adapted to be inserted into a bone anchoring screw adapted to be fixed in said vertebrae to prevent any migration of the intervertebral cage within or outside the intervertebral space.
 30. Device according to claim 29 wherein the complete fixation plate with the small rod connecting the anchoring pins or the locking studs has a piece with a “T” section.
 31. Device according to claim 29 wherein the fixation plate includes an opening at the level of the intervertebral space, said opening enabling the introduction or packing of a graft or bony substitute in the intervertebral space after insertion of the device.
 32. Device according to claim 31 wherein each of the openings of the fixation structure acts together with a bone anchoring screw so that once in place the fixation structure is located in a position shifted relative to a plane containing the axis of the spine.
 33. Device according to claim 27 wherein each of the openings of the fixation structure acts together with a bone anchoring screw so that once in place the fixation structure is located in a position shifted relative to a plane containing the axis of the spine.
 34. Device according to claim 16 wherein the at least one intervertebral cage has, along the axis of the spine, a non-uniform height, the non-uniform height inducing a determined angle between the faces of the vertebrae with respect to the adjacent vertebrae.
 35. Device according to claim 16 wherein at least one of the constitutive parts of the device is made from a radiotransparent material.
 36. Device according to claim 16 further including a fixation structure of the at least one cage for connection to at least one of the vertebrae, the fixation structure being arranged to be added to at least one intervertebral cage by insertion of a projecting part between the small rod and two lugs formed on the device, the fixation structure comprising two legs having adjacent sides forming a “V” shape anchoring tongues connected by a small rod. 